“Sanguis Effectum”: A continued investigation of blood effect theory on the reliability of eye witness recall

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Katie-Louise Peacock

Abstract

Witness testimony is frequently used as a form of evidence within the criminal justice system, as it possesses a high level of evidentiary power (Dando, Wilcock & Milne, 2008), however it is surrounded by much controversy. Weapon focus has been well-documented to reduce the reliability of witness statements, as the witness’ full focus is on the weapon (Loftus, 1966). This results in little attention left to be allocated to details of the crime that do not involve the weapon, such as the victim and the crime scene (Loftus, Loftus & Messo, 1987). Despite an abundance of empirical support, weapon focus theory cannot be generalised to explain low recall rates in non-weapon based crimes. Therefore, it is possible that an alternative explanation for low recall rates can be explained by blood effect theory, which states that blood will act in a similar way to a weapon and draw the witness’ full focus. This results in little or no attention left to be attributed to other factors of the crime, such as the perpetrator and crime scene, reducing recall rates and producing unreliable witness testimonies. Peacock (2014) initially investigated blood effect theory and found that blood significantly reduced recall rates. Inspired by Peacock (2014) findings, the current study employed the use of two experimental conditions; control (N=40) and blood (N=40). Participants were required to watch one of two short video clips and then answer one of two versions of the same questionnaire immediately after, which focused on three key sections; victim, perpetrator and crime scene. Initial statistical analysis suggested that there was a significant effect of section and age on recall rates, but there was no difference in recall rates between the control and experimental condition, suggesting that blood did not have an effect on recall rates as first hypothesised. The results of the current study will be explained by specifically focusing on literature pertaining to blood sensitivity, age, stress, shock and surprise and facial recognition.